Building OCaml Projects with a Flat Directory Structure Using Dune

Learn how to configure Dune to compile OCaml projects organized in a flat directory structure. Get step-by-step instructions to set it up correctly!
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Building OCaml Projects with a Flat Directory Structure Using Dune

Do you want to use Dune to build an OCaml project that has a flat directory structure? If so, you're in the right place! In this guide, we'll break down how to create a project where all your source files exist in the same directory, and we'll explain exactly how to configure your Dune file to achieve this.

Understanding the Scenario

Consider a project layout like this:

[[See Video to Reveal this Text or Code Snippet]]

main.ml serves as the entry point for your OCaml program.

It calls functions from utils.ml, which in turn relies on basics.ml for additional functionality.

You want to access functions in utils.ml using the prefix Utils (like Utils.example_function x y), while keeping a straightforward directory structure without nesting files into subdirectories.

However, many guides show a more complex structure like this, where you segregate libraries into separate folders:

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In this guide, we will focus on how to configure your single-directory structure properly using Dune, without restructuring your project.

Setting Up Your Dune Configuration

To compile your OCaml project successfully with a flat directory structure, you need to specify the modules in your dune file clearly. Here’s how to do it:

Listing Modules in Your Dune File

Open (or create) the dune file in your project folder.

You will need to list the modules as follows:

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Explanation:

The (executable ...) block defines your main executable (main), which consists of the main.ml module and relies on a separate library defined next.

The (library ...) block defines a library mylib that contains the utils.ml and basics.ml modules.

Alternate Configuration: Including All Modules in Executable

If you prefer a more straightforward approach and don't want to create a separate library, you can define your executable to include all the modules directly:

[[See Video to Reveal this Text or Code Snippet]]

Note: In this version, you don’t need to define mylib separately. By compiling all the required modules directly in the executable, you simplify the setup further.

Conclusion

Building an OCaml project with a flat directory structure using Dune is entirely feasible. By carefully structuring your dune file and either defining your modules in a library or directly in the executable, you can keep your project organized while avoiding unnecessary complexity.

If you’re excited about delving deeper into OCaml and Dune, don’t hesitate to experiment with these configurations in your projects. Happy coding!

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